Remote tripping devices or protection signal transmission devices are used for transmitting protection or switching commands in electrical high-voltage and medium-voltage networks and systems, for example for distance protection. Protection commands result, by way of example, in direct or indirect opening of a circuit breaker, and hence in electrical disconnection of a part of the network or of the system. Conversely, other protection commands result in the opening of a circuit breaker being blocked. In a rest case, that is to say when no protection command is being transmitted, a rest signal or guard signal is transmitted continuously instead of this.
Protection commands need to be transmitted, for example, from one section of a high-voltage line to another. To do this, a transmitter in a remote tripping device produces digital signals on the basis of the protection commands, which digital signals are transmitted via a digital signal connection, for example using an E1 (Synchronous Digital Hierarchy, SDH) or T1 (SONET) communication standard. A receiver in another remote tripping device detects the transmitted signals, and determines the corresponding number and nature of the protection commands. In order to ensure transmission despite channel failures, redundant transmission means are provided. In this case, by way of example, the receiver receives on a first channel and, if the channel is interrupted, is switched to a second channel. The switching time which is required for this purpose is, however, 20 ms to 50 ms, which is too long for protection signal transmission. A solution in which each protection device uses two interfaces to separate transmission paths is too complex.